Heretofore, as a spatial optical modulation element employing a surface plasmon resonance, an element has been known wherein on one side of a prism, a metal layer and an optical functional film made of a material with the refractive index changeable by light irradiation (which may be referred to also as a colorant-containing film) are laminated. This element has been reported such that a to-be-modulated light is permitted to enter through the prism and confined or reflected by the metal film, and when it emerges from the prism, a modulation drive light is irradiated to the optical functional film, as the case requires, so that the condition for controlling the to-be-modulated light is changed by ON/OFF of the modulation drive light to make high speed optical modulation practically possible (e.g. patent Document 1 to 3).
Carbon nanotubes have been known to be useful as an is optical functional material. Further, it has been reported that carbon nanotubes have high speed optical response characteristics and the characteristics can be obtained at a wavelength region of from 1 to 2 μm (e.g. patent Document 4 and Non-patent Documents 1 to 3).
Patent Document 1: JP-A-5-273503
Patent Document 2: U.S. Pat. No. 6,611,367
Patent Document 3: JP-A-2002-258332
Patent Document 4: JP-A-2003-121892
Non-patent Document 1: Y. C. Chen et al, Applied Physics Letters, 81, p. 975-977 (2002)
Non-patent Document 2: M. Ichida et al, Physica B, 323, p. 237–238 (2002)
Non-patent Document 3: S. Tatsuura et al, Advanced Materials, 15, p. 534–537 (2003)